RISSOA. 97 



is only composed of five volutions, and is devoid of the 

 longitudinal ribs, has been termed Candida by Brown. Its 

 coils are looser, so that there is often a rudimentary umbi- 

 lical chink, and its texture is thinner, and often of a pale 

 fulvous tint. The acideus of Gould (Invert. Massach. p. 

 266, f. 172, badly) scarcely differs, except in being more 

 umbilicated, and the ardlca of Loveu (Index Moll. Skan- 

 din. p. 24), though a little more flattened horizontally at 

 the top of the whorls, is also too closely allied. The typical 

 specimen forwarded us by the author, has the whorls pro- 

 portionally shorter, and does not exhibit any striro on the 

 extreme base of the shell. 



The body of the animal of this species is less in propor- 

 tion to the shell than that of any other of our native Rissoa;. 

 It is entirely yellowish white. The tentacula are linear, 

 and shorter in proportion to the body than usual in the 

 genus. The eyes are very large and black. The foot is 

 obtusely angulated in front, and similarly pointed behind. 



This is a most abundant shell everywhere in the British 

 seas. It is plentiful in stony and muddy places between 

 tide marks, especially in the neighbourhood of low-water 

 line. It is also common in the laminarian and coralline 

 zones. The greatest depths to which we have known it 

 range, as observed by Mr. M 'Andrew and ourselves, have 

 been twenty-five fathoms, off Penzance, abundant ; thirty 

 fathoms in St. Magnus bay, Zetland, in both instances 

 alive ; and dead shells in fifty fathoms, oiF Mizen Head, 

 S.E. of Ireland ; forty-five fathoms and eighty-two fiithoms 

 off the Zetland Isles. It has evidently a great ca])acity 

 for enduring varying conditions. It is commoner in the 

 north than the south of Europe ; it ranges from Norway 

 to the Mediterranean. It is found fossil in the coralline 

 crag. 



VOL. III. 



